In order to increase recording capacity of an optical information recording medium, attempts have been made on the optical information recording medium for laminating recording layers into a multi-layered structure. As optical information recording media which have been put into practical use for recording information in a plurality of recording layers, write-once digital versatile disks (DVDs) and write-once Blu-ray discs (registered trademark) are already known. However, these media use a one-photon absorption material in the recording layers, with the result that there is a low layer selectivity for causing only a particular recording layer to react upon recording and further that when a far side recording layer is recorded as viewed from a recording beam radiation side, the recording beam is absorbed by near side recording layers. This disadvantageously results in a large loss of the recording beam.
Accordingly, in recent years, attempts have been made to use a multi-photon absorption reaction for the multilayer optical recording medium, in which a reaction occurs only at a limited region in a depth direction upon irradiation of the recording beam, for the purpose of increasing the layer selectivity upon recording while advancing multi-layering (see, for example, Patent Literature 1, Patent Literature 2, and Non-patent Literature 1). Multi-photon absorption reaction is a reaction of absorbing photons which takes place when a recording layer is given a plurality of (e.g., two) photons substantially simultaneously. For example, in a two-photon absorption reaction, light is absorbed proportionally to the square of the intensity of the light, so that the reaction takes place only at a position near the focal point of a beam where the intensity of the light is relatively high, and if a recording beam having a wavelength which does not cause one-photon absorption is used, the near side recording layers allow the recording beam to pass through without causing one-photon absorption. This is advantageous to achieve multi-layering of the recording layer.